The present invention relates to an X-ray CT (computed tomography) imaging method and an X-ray CT apparatus, and more particularly to an X-ray CT imaging method and an X-ray CT apparatus by which the distance of rectilinear motion in a helical scan can be reduced.
As shown in FIG. 29, there is known an X-ray CT apparatus that ensures a constant speed of rectilinear motion in a region of interest ROI by controlling rectilinear motion of a table, the control comprising: appending an acceleration section A before a front end position Ra of the region of interest ROI for which an CT image is to be created to define a rectilinear motion start point La; appending a deceleration section B after a back end position Rb of the region of interest ROI to define a rectilinear motion end point Lb; starting rectilinear motion of the table at a table position at which an X-ray tube 21 looks straight down on the rectilinear motion start point La; increasing the speed of rectilinear motion in the acceleration section A, driving rectilinear motion at a constant speed in the region of interest ROI and decreasing the speed of rectilinear motion in the deceleration section B; and stopping rectilinear motion at a table position at which the X-ray tube 21 looks straight down on the rectilinear motion end point Lb (see Patent Document 1, for example).
It should be noted that in general, the table is rectilinearly moved while rotating the X-ray tube 21 and multi-row detector 24 around a subject to be imaged in a helical scan, although for convenience of illustration FIG. 29 represents the rectilinear motion as if it occurred without rotating the X-ray tube 21 and multi-row detector 24.
[Patent Document 1]Japanese Patent Application Laid Open No. H8-173413.
As can be seen from FIG. 29, the conventional technique appends the acceleration section A before the region of interest ROI and the deceleration section B after the region of interest ROI.
This, however, leads to a problem that the range of rectilinear motion L is longer than the region of interest ROI. Thus, if reciprocal rectilinear motion is conducted, the cycle time becomes longer. Moreover, if X-rays are constantly emitted during rectilinear motion, the exposure dose increases.